Andrew Siegel MD 12/14/19
In recent years, highly sophisticated means of imaging prostate cancer have been developed and put into practice, the topic of today’s entry.
When a diagnosis of castrate resistant prostate cancer (CRPC) is made, imaging studies are important to determine if metastases are present. Accurate staging determines the most appropriate form of treatment, which is targeted to the identified site of metastases. For many years, the best imaging methods for staging prostate cancer and detecting metastases were computerized tomography (CT) and nuclear bone scans. CT and nuclear bone scan have numerous limitations, although CT is useful in detecting the presence of locally advanced disease (seminal vesicle invasion and invasion of surrounding local structures), enlarged lymph nodes and the presence of urinary tract obstruction. Bone scan has traditionally been the most widely used means of skeletal evaluation, often used for initial prostate cancer staging as well as for assessment for recurrence and metastatic disease. A limitation is false positives (bone scan shows abnormality in the absence of metastatic prostate cancer) that often require further imaging studies to evaluate.
Highly sophisticated means of imaging prostate cancer have recently been developed and implemented. The imaging studies available today include magnetic resonance imaging (MRI) and positron emission tomography (PET). MRI has shown value in defining local recurrence following surgery or radiation, particularly helpful in identifying extension of cancer beyond the prostate capsule and seminal vesicle invasion. PET scanning can detect early metastatic prostate cancer by identifying metabolic changes at the cellular level before they become evident on traditional imaging tests. Since the PET scan shows functional changes in the body, it is combined with CT imaging, which shows anatomical details, sites where the functional changes could be occurring. The combined PET/CT scan provides images that localize the abnormal metabolic activity.
PET scans use small amounts of chemicals that cancer cells require to grow and proliferate. These chemicals are “labeled” with radioactive materials. These labeled radio-tracers are injected into the bloodstream where they are taken up to a greater extent in cancer cells than in surrounding normal cells. Any sites of recurrent cancer are identified as bright spots on imaging. These sites in men with a rising PSA following definitive treatment are commonly the prostate bed, lymph nodes and the bony skeleton.
The New-Age Imaging Tests
Choline C11 PET/CT
Cancer cells have an enhanced demand for choline (part of the Vitamin B complex that becomes incorporated into cell membranes) to support their increased metabolism and proliferation. Choline C11 PET/CT uses choline labeled with a type of radioactivity called carbon-11 (C-11). The problem with choline C11 is its rapid rate of radioactive decay with its short half-life (20 minutes) restricting its use to centers that can produce the radio-tracer on site or geographically close by.
Axumin (Fluciclovine F18 labeled synthetic amino acid analog) PET/CT
Cancer cells have an enhanced demand for amino acids (building blocks of proteins) to support their increased metabolism and proliferation. Axumin uses synthetic amino acids that are labeled with a type of radioactivity called fluorine-18. This test is particularly useful for detecting and localizing small recurrences of prostate cancer in men with rising PSA levels following treatment. The much more favorable half-life of F18 (2 hours) makes the Axumin PET/CT much more practical than the Choline C11 PET/CT.
Sodium fluoride (Na-F-18) PET/CT
Cancer cells that have metastasized to bones have an increased demand for certain growth factors and nutrients. Sodium fluoride PET/CT is a “bone-seeking” radio-tracer that is taken up at sites of bone metastases more so than in surrounding normal bone cells, localizing the site and extent of bony metastases. It is a means of accurately detecting bone metastases in patients with advanced prostate cancer, an enhancement over traditional bone scans that can be used as a follow-up study when bone metastases are suspected but not definitive on bone scan.
Prostate specific membrane antigen (PSMA) PET/CT
Prostate specific membrane antigen (PSMA) is a protein found on the surface of prostate cells, normal or cancerous. It is over-expressed in prostate cancer tissue at all stages. PSMA expression is usually low in benign prostate enlargement, increased in prostate cancer and markedly increased with aggressive prostate cancer, CRPC, and metastatic prostate cancer. PSMA PET/CT uses small molecules that bind prostate specific membrane antigen to enable improved staging and accurate detection of metastases in patients with advanced prostate cancer. It is one of the most promising of the different PET radio-pharmaceuticals and is currently available in Europe and under clinical trial in the United States.
Wishing you the best of health,
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Dr. Andrew Siegel is a physician and urological surgeon who is board-certified in urology as well as in female pelvic medicine and reconstructive surgery. He is an Assistant Clinical Professor of Surgery at the Rutgers-New Jersey Medical School and is a Castle Connolly Top Doctor New York Metro Area, Inside Jersey Top Doctor and Inside Jersey Top Doctor for Women’s Health. His mission is to “bridge the gap” between the public and the medical community. He is a urologist at New Jersey Urology, the largest urology practice in the United States.
The content of this entry is excerpted from his new book, PROSTATE CANCER 20/20: A Practical Guide to Understanding Management Options for Patients and Their Families
Video trailer for Prostate Cancer 20/20
Preview of Prostate Cancer 20/20
Andrew Siegel MD Amazon author page
Prostate Cancer 20/20 on Apple iBooks
PROSTATE CANCER 20/20: A Practical Guide to Understanding Management Options for Patients and Their Families is now on sale at Audible, iTunes and Amazon as an audiobook read by the author (just over 6 hours).
Dr. Siegel’s other books:
PROMISCUOUS EATING— Understanding and Ending Our Self-Destructive Relationship with Food
MALE PELVIC FITNESS: Optimizing Sexual and Urinary Health
THE KEGEL FIX: Recharging Female Pelvic, Sexual, and Urinary Health
Tags: advanced imaging techniques, Andrew Siegel MD, Axumin PET/CT, Choline C11 PET/CT, PET/CT, prostate cancer, Prostate Cancer 20/20, PSMA PET/CT, Sodium fluoride PET/CT
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